The Greek Theatre curtain rose at 8 p.m. to reveal a whopping 18 musicians and Duritz, Franti and Augustana frontman Dan Layus swapping verses of Van Morrison's "Caravan." A symbolic and fitting choice, the song set the tone for three joyous hours of musician-trading and record-rewriting, including Duritz as an improbable hype man stalking the stage with hunched shoulders, emphatically throwing hands in the air, waving them carelessly during Spearhead's "Hello Bonjour" and cover of the Temptations' "Don't Look Back," which skillfully meandered into the Grateful Dead's "Casey Jones" territory and back again.

Franti, Spearhead, Crows, Augustana at the Greek

Timothy Norris

The sold-out crowd's yen for '90s nostalgia was sated by the Crows' extended "Long December" piano ballad and banjo, accordion and dual tambourine-bolstered "Omaha." Spearhead's uplifting, fist-pumping run included "Rude Boys Back in Town" and "All I Want is You" before Franti and a two-man rhythm core added Duritz and Layus for defiant new-ish groove "Sound of Sunshine," the solemn yet building "I Got Love for You" and the group's first Top 40 hit, piano-rag ebullient "Say Hey."

Layus and Co. mostly grinned and hung on for dear life through a cover of the Rolling Stones' "Sweet Virginia" and their own Can't Love, Can't Hurt tracks "Fire," "Sweet and Low," "Dust" and "Still Ain't Over You" before acknowledging their major debut with minor wavemaker "Boston."

Timothy Norris

Following a ten-minute intermission, Crows' deep cut "Another Horsedreamer's Blues" was given rare, jazzed-up play thanks to auxiliary saxophone and keys. Juggernaut career-maker "Mr. Jones" raised energy to peak levels, only to plateau with lesser-knowns "Washington Square" and "Goodnight LA." Sure, the latter evoked a few knee-jerk whoops, but it was set closer "Hangin' Around" and all-bands-and-then-some encore of Simon and Garfunkel's "Cecilia," Spearhead's "Hey World," and gospel-ized, accapella-breakdown of "Rain King" that solidified the evening as musical-science experiment gone right. Unfortunately, head-scratching closer "This Land Is Your Land" evoked more incredulity than pride, and even a firm reminder that brotherhood alone won't cover the rent once the circus moves on.